That should be backwards, frankly. We shouldn't subsidize people for building in flood zones and punish people for not building in flood zones.
Idiots who build in flood zones deserve financial ruin. Those that don't need support.
FEMA should only offer flood insurance to those that don't build in flood zones.
Let ordinary insurance companies offer the insurance. I am not for Federal (taxpayer) subsidy of constructing buildings where they are almost guaranteed to be wiped out (NC's Outer Banks, for example).
If people want to build where there are hazards, and the underwriters won't insure them, then they should do so at their own risk, or not at all. There is a reason beach cottages once were simple affairs and generally spartan, not McMansions on the sea.
For some, that inevitably will lead to a loss of real estate, home sites, or homes, but I can see insurers offering flood insurance--all they need are satellite or air photos of the neighborhoods as the water goes down, and they'll be able to map their risk zones.